Process of treating zinc ores.



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rnn strains raunnar on FREDERIECK LAIST, F ANACOIN'lJA, MONTANA, ASSIGNOR T0 ANACONDA COPPER,

MINING COMPANY, ANACONDA, MONTANA, CORPORATION'OIIE MONTANA.

PRUCESS 0F TREATING ZINC ORES.

nann es;

To aZZ whom it may concern:

Be it known that l, FREDERICK LAIST, a citizen of the United States, residing at Anaconda, in the county of 'Deerlodge and State of Montana, have invented certain new and useful improvements in'lProcesses of Treating Zinc Ores, of which the follltl lowing is a specification.

This invention is a process whereby irons free solutions are 'obtainedfrom zincores with a minimum consumption ofthe solvent acid, usually sulfuric acid.

It is the present practice in extracting zinc from blende, for example, to calcine the lib ore at high temperatures, and to leach the ,calcine with dilute sulfuric acid. Some excess of acid 1s us'ed'in order to secure substantially complete extraction of the zinc,

with the result that the solutions obtained contain iron, which is precipitated. in the ferric state by neutralizing the excess acid by means of calcine, with or Without the final till addition of a; little limestone, the solution being subjected to oziidation at some stage of the operation to convert all of the iron into the ferric state; Under these conditions, arsenic is precipitated in combination with the'iron. The solution is now filtered, th'e'filtrate being subjected to further purifying operations and ultimately to az in'c-'re-- covery process, while the ferric precipitate," which in addition to its arsenic content 'con-.

tains considerable sulfate of zinc, is rer turned to the ore-calcining furnaces for. the purpose of rendering the iron ll'lSOllllllQlf Alt 3 the high operating temperature of thesefunnaces, the bulk of the zinc sulfate" is of course decomposedythe equivalent quantity 1 loss of acidmay be largely or entirely avoid- Speciflcation of lletjtcrs latent. Patented lFiEEllllm 5, into, Application filed nu id, 1916. Serial No. ioaaci.

ed, while at the same time eflecting a sepa- ,-rationof the iron, by modifying the aboyedescribed process as follows: The ore is calcined and leached ,as usual, the calcination taking place at high ternperatures and the requisite excess of the acid i solvent being employed for leaching. After.

separating the residue from v the solvent by filtration or otherwise, the solution is neuexcess of oalcine.

This residue is now roasted in any suitable furnace operating at a controlled temperature materially ,below that of the regular calciningrfurnaces, the furnacing conditions,

including thetemperature and time of heating,-beingregulated with a View to rendering the iron insoluble in dilute acids while avoiding any materialdecomposition of zinc sulfate; gliorthis purpose the temperature should not enceed 625 C. i'llhe product from this'furnace is preferably addedto the recovered, l

ner' the losses ofsulfuric acid are greatly ore, leaching thecalcine with asolution con taining sulfuric acid, precipitating the iron from the resulting solution by wnnaterialjcontaining fzinc'oaid, separating the precipitate 'froin. the iron-free solution, fur--- nacing .said precipitate at a temperature 4 materially below that of the calcination, said temperature 'sutlicient to render the ferriccompounds insoluble .while avoiding sub- By conducting the operation this mancalcine from theregular roasting furnaces, and passes with the jcalcine through the leaching step,i-whereby' its zinc content is x taiiiihg iron, which consists in calcining the stantial decomposition of zinc sulfate, and tion point of zinc sulfate, and extracting 1a extracting the zinc sulfate from the furthe zincv sulfate from the furnaced product.

naced product. In testimony whereof I aflix my signature 2. In a process of treating calcined zinc in presence of two witnesses. 5 ores, the steps which consist in precipitating FREDERICK LAIST iron from impure zinc sulfate solutions by a,

material containing zinc oxid, furnacing the Witnesses: precipitate at a temperature below that of ALBERT E. WIGGIN, the calcination and below the decompo'si- JAMES McPnERsoN'. 

